I have gotten it working in PPP and LTE mode, so it's possible. I'll write up what I know in case that helps.
If it doesn't show up as an LTE modem, the "at-chat" option isn't the only way to issue AT commands, which I think is your problem since it's a catch-22 if the module isn't in ECM mode, it won't show up as LTE, and if there isn't an LTE interface "at-chat" don't work.
But you can always use "/system serial-terminal port=XXX channel=X" to enter the commands from the Quectel wiki page; if you use "/ports print" you'd get the need port#, and I think it its channel=0 but you can try multiple ones. From the serial-terminal to the card you should be able to enter the AT commands mentioned to set the CDC mode (e.g. PPP or LTE in Mikrotik terms, or PPP or ECM in USB driver world
But you may not want LTE mode as the card will act as it own router and do it's own NAT'ing on the miniPCIe, outside of the Mikrotik firewall (e.g. after the Mikrotik routing plane). This wasn't helpful in my case, since I had a static IP address I wanted available to the Mikrotik, so I ended up using PPP mode. Now would have rather used LTE mode (to avoid the ~30Mb/s limit of PPP), but Quectel support told a few months ago: "With ECM mode (AT + QCFG = "usbnet", 1) [e.g. LTE mode on Mikrotik], the connection will work via NAT, so the module will provide it's own local ip address to mikrotik (not the network one)".
For completeness, the USB integration modes available on the EC25 are:
AT+QCFG="usbnet",0 - is PPP & QMI (default)
AT+QCFG="usbnet",1 - is ECM.
AT+QCFG="usbnet",2 - is MBIM
While Quectel EC25 supports QMI and MBIM mode, neither are currently supported by Mikrotik. MBIM mode is what ROS v7 is promised to bring, and would make this a lot easier than AT commands. PPP mode is what I'd recommend, but you can get working in LTE mode if you use /system serial-terminal to set the needed AT+QCFG="usbnet",1 command if you want to try, and you can use AT+QCFG="usbnet",0 to get it back to working in PPP mode.
Finally, if you need to get RSRP, SINR, or RSRQ from the module, then use AT+QENG="servingcell".
Hope this helps.